Game idea feedback

I have an idea for a game. I wrote the game quite a few years ago when .NET 1.0 was first released so I could learn it. I've ported that to the iPhone in an effort to learn developing for iPhone (it was my first attempt for any OS X development). Now that I have it ported and mostly working, I was thinking it'd be better to redo the whole game now that I've got a better grasp on programming in general and the iPhone in particular. I was just wondering if it was worth rewriting the game or if I should start on a completely new one.

The game is Missile Command with a twist. I write stock trading software, so I came up with MetaStock Command. Stock charts (line, bar, and candle) are plummeting down and blow up your piles of cash, so you have to shoot missiles up to stop them. It's mostly done in that I have an NSMutableArray that I wanted to put the CGPoints in for bar and candle chart drawing, but can't. So, I need to do those two types. Other than that and the line chart is a single dot and no line (also due to the problem with the CGPoints), it works and it looks pretty good.

So, what do you guys think? Sound interesting or should I work on a different game? I had other thoughts to add onto this game, such as multiplayer on two devices, but not sure how fun that'd be. My thought on that was one player controls the incoming missiles, maybe as simple as just picking which money pile or missile launcher to strike or maybe with a flick or something, can slightly alter the speed of the missile while the other player plays as normal, trying to blow up the incoming missiles.

I tried to piece an image together in my head from your description, but it didn't work completely, so I will describe my own version of your idea, which you are free to steal. And you better steal it, because if you don't, I might.

I see a continuously scrolling environment that looks like a stock chart. At the bottom you have a Product Cannon and a PR Cannon. The Product Cannon has more power, but the PR cannon has more ammo. On Level 1, you only have to worry about the stock of one company. On Level 2, you're CEO of two companies, etc. Things come out of the "sky" such as corrupt executives, recalls, safety hazards, and bad press that either start downward trends or just bump the line down. If it hits the bottom, that company goes bankrupt. If you lose all companies, you lose the game. Occasionally, horizontal stock price target lines appear, and if you can beat them in a certain amount of time (10 seconds?) you get extra points, like being in the Fortune 500 or winning some industry award.

Harder difficulty levels could just make things go faster. Not all product/PR ammo should be equal - there should be some random variation, since not all ideas are great ones. Maybe some of your ammo could back fire and take your line down a little bit.

I'd do a mockup right now, but I'm at work. Things to do, you know.

EDIT: I've changed my mind about variable product/PR power. They would explode at their targets like Missile Command, so if you aimed high you would actually knock your line down. The 2-player game could just have 2 lines, with players trying to both push their own line up and the other guy's down.